Resistor cell circuit



C. F. JENKINS RESISTOR CELL CIRCUIT Filed Oct. 22. 1924 F J N Patented Nov. 27, 1928;

outrun sures masses earaur castes;

CHARLES FRANCIS JENKINS, OF WASHINGTON, DISTRICT OF COLUMBIA.

RESISTOR CELL CIRCUIT.

Application filed October 22, 1924. Serial No. 745,215.

This invention relates'to radio circuits in which a light-sensitive cell is employed to modulate thecircuit, and its principal object is to so control the circuit as to interrupt a Wave as though it were key modulated. I

With this and other objects in view,jthe arrangement of the elements of the circuit is described herein, illustratedin the drawing, and particularlypointed out in the claim.

The'whole is a system for controlling an oscillator of radio frequency by the action of light on alphoto-electric cell. It employs a resistance-coupled amplifier to amplify the direct current efi'ect of changing light on the a cleanoil-and-on of the plate current in the last tube of the amplifier, and this tube acts as a valve or key in the circuit of the oscillator.

Inthe drawing A is a light-sensitive cell;

3 a battery and G a resistance, both in circuit with the cell, E a detector tube; F a bat- 4 tery and G a resistance, both in the plate circuit of the tube E; H is a filament battery;

J a bat-te ryiinthe grid circuit of amplifier tube K. Lv is a battery in the plate circuit of amplifiertube K. The plates of amplifier Y tube K and oscillator tube M are in series,

the oscillatorcurrent being by-passed through condenser N. .1 In operation, light falling on the cell A varies the electric current in the cell circuit which disturbs the static condition of the grid circuit." This ellect is amplified, and intion of the tube being resumed as-soon as the original conditionof the cell A is restored.

- If, then, typewritten or hand-writtenletters (black on white paper, for example) were made to cross the light cell, or any other means were employed to cut the light ofi and on the cell, the intermittent eifect of the light on the cell would react to interrupt the 0s cillation of the transmitter.

As a result of Ion continued experiments A in my laboratory, I ave'discovered that the terrupts the oscillation of tube M, the oscilla eassura use of an audio-amplifying method with a ting and receiving systems within at least the short wave and broadcast meter bands, and further that this method of amplification provides in connection with a method of modulation of the character set forth, to wit, plate modulation, a combin ationof amplifying and modulating methods whereby an efi'ective operating condition is established for a clean,

sharp cut-0H action, equivalent to that secured by key-controlledmodulation; By this means, as has been demonstrated both by my laboratory experiments, and by actual picturebroadcasting from my station 3XK, the production of strong and sharply defined signals for long distance radio transmission of blackand white images is rendere'dpossible to obtain at the receiver pictures which are very clear and distinct and sharply bordered and free from fringe effects due to la and other defects incidental to ular cut-oif actions.

What I claim, is- I In a radio amplifier and modulator, a light sensitive cell, a three-element tube, a IBSlStance coupling between said cell and tube, an amplifier, a resistance coupling between said tube and amplifier, a source of potential in circuit with the cell and grid of the tube,

sources of potential located respectively in" the plate circuitof the tubeand grid circuit of the amplifier on opposite sides of the second-named resistance coupling, an oscillating ductor between said source of potential there in and the plate ofthe oscillating tube.

. Intestimony whereoi I have aflixed my signature,

\ r was matters JENKINS.

slow and irreg- 

